Stripe domains in thin magnetic films and their application to display-memories

A new technique for information display [1] is described which makes use of a microdomain structure existing in a certain class of thin magnetic films. The display element consists of a planar, hermetically sealed unit containing an RIS 1 magnetic film and an overlying colloidal suspension of iron oxide. The effect of the "stripe" domain structure of the magnetic film upon the colloid is such as to furnish an element which is capable of diffracting light incident upon the surface of the element in a manner similar to that of a diffraction grating. The interference phenomena are, however, controllable by a magnetic field applied to cause changes in the distribution of the magnetization within the film. Both the intensity and color of the diffracted light can be modified by the applied field and such modification, once produced, is permanent until subsequent alteration is required. Command of the element can be accomplished by coincident drive currents in matrix fashion as is common in the operation of planar magnetic memories. Electrically selectable gray scale and color can be achieved. In addition to the display capability of the element, there is the possibility of utilizing the enclosed magnetic medium as a memory store. The feasibility of making manual entries of information into the memory-display has been demonstrated as well. Several means of writing into and reading from the elements are discussed. Measurements performed on experimental RIS 1 display panels indicate a brightness of over 30L and a contrast ratio of greater than 70 to 1. Display element switching times of the order of 30 ns and image formation times of approximately 10 ms have been measured.